Generation of ions in high pressure high velocity gas stream



u 1.: 3 1 0 *1 1 SR FIPSSOZ GR 3 439197 A ril 15, 1969 H. J. P. VONOHAIN ETAL 3, 7

GENERATION OF IONS IN HIGH PRESSURE HIGH VELOCITY GAS STREAM Filed Feb.16, 1967 To sup/=49 OF /95 (M1062 HIGH P49635026 United States Patent[7.8. Cl. 310-11 3 Claims ABSTRACT OF THE DISCLOSURE Inelectro-fluid-dynamic power conversion apparatus, limits of pressure anddensity of the ion transport gas are reached where the desirable coronadischarge for generating ions breaks down into a spark or plasma typedischarge. To avoid this condition, the gas duct is constructed toinclude an electrically conducting expansion nozzle, charged to a highelectrical potential and also serving as an attractor electrode. Acorona generating electrode is positioned adjacent the throat of theexpansion nozzle and is heated to a high temperature. I11 the boundarylayer in the immediate vicinity of the corona electrode, due to the hightemperature, there exists a zone of relatively low gas density andcorrespondingly low breakdown field strength. An abundant stream ofunipolar ions can then be pulled into the gas stream from the heatedcorona electrode by the attractor electrode potential and be sweptdownstream in the jet discharge of the expansion nozzle.

The invention described herein may be manufactured and used by or forthe United States Government for governmental purposes without paymentto us of any royalty thereon.

The invention relates to improvements in electro-fiuiddynamic powerconversion apparatus of the type disclosed in United States Patent3,225,225 issued 'Dec. 21, 1965. In the patented power generatingsystem, ions are seeded into a high velocity gas system and the ions areaccelerated by the gas molecules at the expense of the energy of the gasstream. Doing work on the ions corresponds to an increase in theirelectrical potential with respect to ground and the charged particlesgive up their electrical charges to a collector electrode assembly. Thecollector electrode assembly at a high potential is connected to anexternal load circuit. In order to increase the electrical powergenerating capacity of the patented system, it is essential to generatelarge quantities of unipolar ions or charged particles in very densehigh velocity gas flows. It is well known that unipolar ions can begenerated by a corona discharge. However, when the transport gas densityis greatly increased with respect to atmospheric conditions, it reachesa level at which the corona discharge phenomena discontinues ratherabruptly in spite of an extremely high electrical potential between thecorona and attractor electrodes. The desirable corona discharge breaksdown into a spark or plasma arc type discharge when the limitingconditions are reached, which interrupts the ion generation.

It is the object of the present invention to remove the upper densitylimitation heretofore present in electric power generating of the typedescribed. In accordance with the invention, a very effective coronadischarge can be obtained even under extremely high gas densityconditions where normally only spark discharge can be ob-- tained. Howthis desirable objective is obtained is as follows. An expanding gasflows through a nozzle which is made of an electrically conductingmaterial and connected to a source of high electric potential. Theexpansion nozzle serves also as an attractor electrode. The coronagenerating electrode is positioned within the expansion nozzle and isconstructed so that its external surface, or at least the tip is heatedto a high temperature, for example, electrically. Even under extremelyhigh gas pressure conditions, by this arrangement an abundant supply ofunipolar ions or other charged particles will be released from thecorona electrode by the combined effects of (a) extremely highelectrostatic field strength concentration at the surface of the coronaelectrode and (b) high corona electrode temperature with associated lowlocal gas density with correspondingly low breakdown field strength inthe immediate vicinity of the heated electrode surface.

Other more specific features of the invention will become apparent byreference to the detailed description hereinafter given when taken inconjunction with the appended drawings, in which;

FIG. 1 illustrates a longitudinal sectional view of an ion generatingequipment in accordance with the invention; and

FIG. 2 is a view similar to FIG. 1 illustrating a modified coronaelectrode in the shape of a ring.

With reference now to FIG. 1, the reference numeral 1 generallyindicates a duct adapted to conduct a gas at high pressure, for example,of the order of atmospheres. The duct has a tubular metal entranceportion 2 adapted to be connected to a source of gas under high pressure(not shown). The gas may, for example, be high pressure steam, air,carbon dioxide, metal vapors and the like. The duct portion 2 connectsto a hollow electrically insulating section 3 which may, for example, bemade of a ceramic liner portion covered by resin impregnated fiberglassto withstand high pressure. The duct section 3 contains a cylindricalinsulating support 4 adapted to house electrical conductors 6 which areconnected by high temperature brazing or the like to a conical metal tip8 made from a high resistance metal alloy so as to be heated to a hightemperature when an electric current is passed therethrough. Theconductors 6 are adapted to be connected in series with the tip 8 to anexternal source of electric current, for example, the battery 10, byconductors 11 and 12 and the heater circuit being electrically groundedas indicated at 14.

The insulating duct section 3 connects on its downstream side to anozzle section 15 made of metal or other electrically conductingmaterial. The nozzle section 15 is internally contoured into aconvergent entrance section 16, a throat 17 and a divergent diffusersection 18. The nozzle section 15 of the duct 1 is electrically connected by a conductor 19 to a source of high voltage direct current 20which is suitably grounded, as indicated at 21 to form a grounded returncircuit to the corona electrode 8. The high voltage power supply 20,which can be of the well known step-up alternating current transformerand rectifier type, may supply an attractor electrode voltage of theorder of 50,000 volts D.C.

Downstream from the nozzle section 15, the conduit 1 consists of aninsulating section 25, which serves to conduct the high velocity gasstream seeded with positive ions or charged particles to a collectorelectrode section (not shown) similar to that disclosed in our patentedpower generation device, U.S. Patent 3,225,225, previously noted.

The system disclosed in FIG. 1 operates as follows. A suitable transportgas under high pressure is delivered from a source (not shown) into theinlet end of the section 2 of the duct system generally indicated by thereference numeral 1 and flows through the insulating section 3 of theduct 1 into the inlet portion 16 of the expansion nozzle 15 and flowsthrough the nozzle throat 17 where the gas velocity is sonic. When thenozzle 15 is charged by the power supply 20 to a high negativeelectrostatic potential, the field created at the heated tip of thecorona electrode results in the production and the acceleration ofpositive ions into the high velocity gas stream at or near the nozzlethroat. The ions are swept downstream through the eXpanding section 18of the nozzle to ultimately be collected on collector plates (not shown)in the manner as illustrated and described in our Patent No. 3,225,225,previously noted.

During operation, the corona electrode tip 8 is continuously heated bycurrent through conductors 6, 11 and 12 from battery or other directcurrent source. By thus being heated to a high temperature, the gasboundary layer in the vicinity of the electrode will be reduced indensity permitting a copious flow of positive ions at high streampressures and densities. The invention accordingly makes it possible togreatly increase the electrical power output capacity of equipment ofthe type as described in our prior Patent No. 3,225,225 by making itpossible to have copious ion generation at greatly increased transportgas pressure and density.

FIG. 2 illustrates a structure similar to FIG. 1 except that the coronaelectrode is in the form of a ring. As seen in FIG. 2, the cylindricalinsulating corona electrode holder indicated by the reference numeral 4is provided with a streamlined nose portion 4a of smaller root diameterthan that of the holder 4 leaving an offset or recess 30 formed with agroove 32 which is semicircular in cross section. The groove 32 isadapted to receive a ring-shaped electrode 35, which may be in the formof a complete circle except for a single gap. The ring electrode 35 ismade of high resistance metal alloy and adapted to be heated to hightemperature by direct current applied from an external source byconductors 6 similar to FIG. 1. If desired, the ring electrode 35 may behollow and indirectly electrically heated by a heater coil (not shown)positioned within the electrode. The electrode 35 serves the samefunction as the corona electrode 8 of FIG. 1. The streamlined noseportion 4a of the corona electrode holder 4 serves to form with theattractor electrode 15 a diverging section 18 of the expansion nozzle.The ring electrode 35 is positioned at or near the throat section 17 ofthe nozzle 15. The offset or recess serves to provide a sheltered zonefor the ring electrode so that a high temperature gas blanket willsurround the exterior of the ring electrode 35 and provide for easyescape of ions with a broader angle of distribution than from electrode8 of FIG. 1 and also providing a more stable corona discharge.

We claim:

1. In an electro-fluid-dynamic power conversion apparatus of thecharacter described, a conduit adapted to be connected to a source ofhigh pressure gas or vapor, a

nozzle in said conduit, said nozzle having inlet, throat and divergingsections, said nozzle being adapted to expand the flow of gastherethrough to substantially sonic velocity or higher, said nozzlehaving at least the inner portions thereof made of an electricallyconducting material, said nozzle being electrically insulated from theother portions of said conduit, a source of high electrical potential,the conducting portions of said nozzle being connected to said source ofhigh electrical potential and serving as an attractor electrode, acorona electrode positioned within said conduit adjacent the throatsection of said expansion nozzle, said corona electrode adapted tocooperate with the attractor electrode to cause a corona dischargetherebetween and means for heating said corona electrode to a hightemperature while the high pressure gas stream flows thereover.

2. The structure as claimed in claim 1, in which the corona generatingelectrode is a high resistance electrically conducting materialsubstantially of conical shape with the tip portion positionedsubstantially at the throat section of the expansion nozzle, electricalconductors supported within and insulated from said duct and connectedto said corona generating electrode and an external electric circuitconnected to said conductors and including a power source and aconnection from said external circuit to ground.

3. The structure as claimed in claim 1, in which the corona generatingelectrode is substantially ring-shaped and positioned substantially atthe throat of the expansion nozzle which serves also as an attractorelectrode, a substantially cylindrical insulating support positionedwithin said duct with its longitudinal axis concentric with saidexpansion nozzle, said cylindrical support having a streamlined nosesection having a base diameter smaller than the diameter of thecylindrical support to form an ofiset portion, a semicylindrical groovein said oifset portion housing said corona generating electrode and saidelectrode being sheltered from direct contact with the high pressure,the high velocity gas stream and conductors connecting said coronaelectrode to a source for heating the corona electrode to a hightemperature.

References Cited UNITED STATES PATENTS 3,129,157 4/1964 Loeckenhoff 204l3,225,225 12/1965 Wattendorf et al. 3106 DAVID X. SLINEY, PrimalExaminer.

U.S. Cl. X.R. 3l06

